This invention relates to a motor vehicle seat belt retractor and particularly to a retractor which can be operated both as an emergency locking retractor or an automatic locking retractor.
Most motor vehicles are equipped with seat belt systems which act to restrain the occupants when the vehicle is subjected to high rates of deceleration which may occur, for example, during a collision. Many seat belt retractors are of the so-called emergency locking variety. These retractors employ an inertia sensitive actuator which prevents seat belt webbing from being withdrawn from the retractor when the vehicle is subjected to deceleration forces above a predetermined level, thereby restraining the vehicle occupant. During normal operating circumstances, however, the seat belt webbing may be freely withdrawn from the retractor, providing freedom of movement of the occupants.
Another type of seat belt retractor is often referred to as an automatic locking retractor. When using these retractors, the seat belt webbing is fully withdrawn from the retractor and, as webbing is thereafter retracted, a locking bar engages sprockets within the retractor thus preventing withdrawal. These retractors therefore act as a one-way clutch once the webbing is fully withdrawn, permitting webbing to be retracted within the retractor but not withdrawn. When, however, the seat belt is unfastened and the webbing is fully retracted within the retractor, the webbing can again be withdrawn to the desired extent. These types of retractors tend to firmly restrain the occupant since webbing cannot be withdrawn and therefore restrict freedom of movement of the occupant.
The emergency locking retractor design has many advantages in terms of occupant comfort and convenience, since they permit free movement of the occupants until deceleration forces above a predetermined level are sensed. Emergency locking retractors, however, have been found undesirable when used to fasten a child restraint system within the vehicle. For this application, it is preferred that the seat belt system firmly and securely anchor the child restraint system to the vehicle. Since automatic locking retractors do not permit free withdrawal of webbing, they are preferable for anchoring a child restraint system within the vehicle.
Due to the conflicting needs to provide adult occupant comfort and convenience, and the need to securely fasten child restraint systems within vehicles, it is desirable to provide a dual mode seat belt retractor assembly which may be converted between emergency locking and automatic locking operation in accordance with the needs of the user. It is therefore a principal object of this invention to provide such a dual mode seat belt retractor. It is a further object of this invention to provide a dual mode retractor which is easily switched between operational modes. It is yet another object of this invention to provide a dual mode seat belt retractor which is simple in design and inexpensive. It is yet another object of this invention to provide a dual mode retractor having an automatic locking mechanism which is independent of the emergency locking inertia actuator, thereby not adversely affecting reliability of the emergency locking feature of the retractor.
The above principal objects of this invention are achieved by providing a seat belt retractor having an actuator cam attached to the rotating retractor spool. An actuator lever is employed which engages the actuator cam in one position to urge the locking bar into engagement with the toothed sprockets of the retractor spool to provide automatic locking operation, and is disengageable with the cam to provide emergency locking operation. The actuator lever is moved between these two operational mode positions through rotation of a drive plate which includes a pair of cam surfaces which urges the actuator lever between the operational positions. The drive plate is caused to rotate by locating an idler gear thereon which is caused to rotate around a retractor shaft gear and meshes with the retractor shaft gear and a fixed ring gear. The drive plate is arranged so that the retractor switches to automatic locking mode when the webbing is nearly fully withdrawn from the retractor. The retractor returns to emergency locking retractor once webbing is fully retracted.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.